Research on the technical adaptability of magnesium hydroxide in the process of superconducting cable industrialization
In recent years, with the transformation of the global energy structure to low-carbonization, superconducting cable technology has become a research hotspot in the energy field due to its high-efficiency and low-loss power transmission characteristics. In the process of superconducting cable industrialization, the importance of material science has become increasingly prominent. Among them, magnesium hydroxide (Mg(OH)₂), as a key functional material, has shown irreplaceable technical adaptability in insulation, heat dissipation, flame retardancy and other aspects due to its unique physical and chemical properties. This article deeply explores the adaptability value of magnesium hydroxide in superconducting cables from the dimensions of material performance, application scenarios and industrialization challenges.
1. Matching the material properties of magnesium hydroxide with the needs of superconducting cables
Superconducting cables need to operate at extremely low temperatures (usually liquid nitrogen temperature zone, about -196°C), and at the same time need to withstand high voltage and high current transmission environments. This places strict requirements on the insulation, thermal stability and mechanical strength of the material. As an inorganic compound, the properties of magnesium hydroxide are highly consistent with the core requirements of superconducting cables:
1. Excellent insulation performance
The dielectric constant (ε≈8.5) and volume resistivity (>10¹⁴ Ω·cm) of magnesium hydroxide make it an ideal insulating material. In the multilayer structure of superconducting cables, the magnesium hydroxide coating can effectively isolate the conductor from the external environment and reduce the risk of leakage.
2. High thermal stability and heat dissipation capacity
When superconducting cables are in operation, local overheating may cause quenching, which in turn destroys the superconducting state. The thermal conductivity of magnesium hydroxide (about 30 W/m·K) is significantly higher than that of traditional polymer insulation materials (such as polyethylene, 0.3 - 0.5 W/m·K), which can quickly dissipate heat and improve system stability.
3. Flame retardant and environmentally friendly properties
Magnesium hydroxide decomposes at high temperatures to produce magnesium oxide and water vapor. This process can absorb a large amount of heat and dilute the oxygen concentration, giving the cable self-extinguishing ability. At the same time, its non-toxic and halogen-free properties comply with EU RoHS and other environmental standards, avoiding the environmental risks of traditional flame retardants.
2. Specific application scenarios of magnesium hydroxide in superconducting cables
In the manufacture of superconducting cables, magnesium hydroxide is mainly used in the following links:
1. Optimization of insulation layer materials
Traditional superconducting cables often use polymer insulation layers impregnated with liquid nitrogen, but they are prone to brittle cracking at low temperatures. Studies have shown that doping magnesium hydroxide nanoparticles (particle size <100 nm) into a polyethylene matrix can increase the tensile strength of the insulation layer by 40%, and still maintain flexibility at -196°C (data source: IEEE Transactions on Applied Superconductivity, 2022).
2. Development of flame-retardant coatings
For the application needs of superconducting cables in high-density scenarios such as data centers and urban power grids, magnesium hydroxide flame-retardant coatings can be covered on the outer layer of the cable. Experiments show that adding 30% magnesium hydroxide coating can increase the limiting oxygen index (LOI) of the cable from 18% to 32%, and the flame retardant grade reaches UL94 V-0 standard (Source: Materials Science and Engineering B, 2023).
3. Interface enhancement in low temperature environment
The interface bonding strength between superconducting tape (such as YBCO or BSCCO) and metal substrate directly affects the current carrying capacity of the cable. By treating the substrate surface with magnesium hydroxide nanosol, a micron-scale rough structure can be formed, which increases the interface shear strength by 25% (experimental data: Superconductor Science and Technology, 2021).
III. Technical adaptability challenges and solutions
Although magnesium hydroxide has significant potential in superconducting cables, its industrial application still faces the following bottlenecks:
1. Nano-scale dispersion problem
Magnesium hydroxide particles are easy to agglomerate, resulting in local defects in the insulation layer. Solutions include:
- Surface modification technology: Use silane coupling agent to coat the particles to improve compatibility with polymers.
- In-situ synthesis method: Directly generate magnesium hydroxide nanocrystals in the polymer matrix to avoid the problem of uneven dispersion of mechanical mixing.
2. Phase change control in low temperature environment
Magnesium hydroxide may undergo lattice distortion at -196°C, affecting insulation performance. Studies have shown that by introducing alumina (Al₂O₃) as a stabilizer, the phase change temperature can be reduced to -210°C, which is fully compatible with the liquid nitrogen temperature zone (data source: Journal of Alloys and Compounds, 2023).
3. Large-scale production cost control
The preparation cost of high-purity magnesium hydroxide is relatively high. The current industry trend is to use industrial by-products (such as magnesium slag after lithium extraction from brine) as raw materials, and synthesize high-purity Mg(OH)₂ by acidolysis-hydrothermal method, which reduces costs by more than 30% (case: China Qinghai Salt Lake Group pilot project).
IV. Prospects of technical routes in the process of industrialization
In the next 3-5 years, the application of magnesium hydroxide in superconducting cables will focus on the following directions:
- Development of multifunctional composite materials: combining two-dimensional materials such as graphene and boron nitride to construct composite coatings with insulation, thermal conductivity and electromagnetic shielding properties.
- Intelligent manufacturing process: using 3D printing technology to achieve precise deposition of magnesium hydroxide coatings and improve the consistency of cable structures.
- Full life cycle assessment: establishing a green industrial chain from raw material extraction, production to recycling to reduce carbon emissions.
With its unique combination of properties, magnesium hydroxide has become an indispensable functional material in the industrialization process of superconducting cables. By optimizing the material preparation process, solving the problem of low-temperature adaptability and combining intelligent manufacturing technology, magnesium hydroxide is expected to promote the large-scale application of superconducting cables in the fields of power grid upgrades and new energy grid connection, and provide key technical support for global energy transformation. With the deepening of industry-university-research cooperation, the potential of this material will be further released, helping superconducting technology move from the laboratory to real scenes.